Optimus questions/problems with my M11X

Hey guys, I received my laptop 2 days ago, and today I decided to try playing some games on Steam, but the problems is, it won't recognize my discrete graphic card, only the integrated one, and it will also block me from playing some games, saying I don't have the required configuration while I know the 335M is powerful enough to play them.  I find this weird because Dell lets us decide if we want Steam preinstalled, so I tought they would have arranged it to make it work.  I was also wondering if there was a way to tell, other than by looking in the nVidia control panel, if the discrete card or the integrated one is on, because I don't hear any differences when I activate either one of them in the control pannel nor any resolution or screen quality changes.  Thanks in advance for your answers.

-Simon